Horizontal mercury cells

ABSTRACT

DESCRIBES A HORIZONTAL MERCURY CELL INCLINED BETWEEN 0.1 AND 1.9* FROM THE HORIZONTAL WHICH IS PREFERABLY EQUIPPED WITH EITHER DIMENSIONALLY STABLE ANODES OR GRAPHIC ANODES, HAS EITHER A RIGID OR FLEXIBLE CELL COVER AND IS OPERATED AS A FLOODED CELL, SUBSTANTIALLY FILLED WITH ELECTROLYTE.

swt. s, 1972 Filed Deo. 4, 1969 A. l.. BARBATO ETAL HORIZONTAL MERCURY CELLS.

5 Sheets-Sheet l FIGLZ INVENToRs RICHARD :.LoFmELo HENRY wiwn I Sept. 5, 1972 A. BARBA-ro ETAI- 3,589,384

HORIZONTAL MERCURY CELLS.

Filed Dec. 4, 1969 5 sheets-sheet a Sept. 5, 1972 A. l.. BARBATO El' AL 3,689,384

HORIZONTAL MERCURY CELLS.

5 Sheets-Sheet 3 Filed Deo. 4, 1969 SPt- 5, l972 A. l.. BARBATO ETAI- 3,689,384

HORIZONTAL MERCURY CELLS.

5 Sheets-Sheet 4.

Filed Dec. 4, 1969 F|G.7 53o FIG.8

Cso

www 2 SPL 5 1972 A. L. BARBATo ErAL 3,689,384

HORIZONTAL MERCURY CELLS Filed Dec. 4, 1969 5 Sheets-Sheet 5 F|G.II

INVENTORS RICHARD E.LOFTFIELD HENRY W. LUB BY ALE XANDERLBARBATO PUnited States Patent O 3,689,384 HORIZGNTAL MERCURY CELLS Alexander Louis Barbato, Perry, Ohio, Henry William Laub, Pasadena, Tex., and Richard Eric Loftield, Chardon, Ohio, assiguors to Electrochemical Industries Corporation, Chiasso, Switzerland Filed Dec. 4, 1969, Ser. No. 882,030 Int. Cl. B01k 3/06; C01d 1/12; C22d 1/04 U.S. Cl. 204-99 17 Claims ABSTRACT F THE DISCLOSURE Describes a horizontal mercury cell inclined between 0.1 and 1.9 from the horizontal which is preferably equipped with either dimensionally stable anodes or graphite anodes, has either a rigid or flexible cell cover and is operated as a ooded cell, substantially filled with electrolyte.

This invention relates to improvements in horizontal mercury cells of the type in which mercury flows over a cathode base plate which is only slightly inclined from the horizontal. The normal inclination of horizontal mercury cells is between about 0.25 to 0.5 from the horizontal. However, the improvements described in this application relate to horizontal mercury cells in which the cathode base plate may be inclined as much as 1.9 to the horizontal. The term horizontal mercury cells as used herein is meant to apply to cells having an inclination of the base of between 0.1 to 1.9 from the horizontal plane. It also relates to mercury cells having a greater inclination than l.9 from the horizontal when operated as flooded cells with flexible cell covers.

We have found that it is possible to operate horizontal mercury cells as defined above substantially filled with electrolyte so that these cells can b e operated as Hooded cells. Operation as flooded cells gives many advantages over the normal horizontal cell operation in which the electrolyte only partially fills the cell box and leaves a gas space over the entire electrolyte surface between the top of the electrolyte and the cell cover.

We have also found that with flooded cells and the free escape of gas bubbles from beneath the anode surface, through the perforations of the anodes and around the edges thereof, the electrolyte can be kept in a high state of agitation and circulation within mercury cells, so that differences in temperatures and composition of the electrolyte from end to end of the cell are practically eliminated.

The anodes used in the cells may be graphite, graphite with holes therethrough or dimensionally stable anodes consisting of a valve metal base such as titanium or tantalum with a coating thereon of more conductive material having electrocatalytic properties.

As a result of our discoveries, the cells can be operated without a material temperature differential between the inlet and the outlet end of the cells and the cells can tolerate a higher amount of impurities in the electrolyte and can, therefore, be operated with less pure brine and the cost of the purification plant and the expense of purifying brines for use in these cells can be greatly reduced.

3,689,384 Patented Sept. 5, 1972 ice forarninous dimensionally stable anodes through which gas bubbles may freely escape are used, many of these advantages are also realized when graphite and especially perforated and slotted graphite anodes are used. The advantages of our invention become more pronounced, when dimensionally stable anodes such as exemplified by titanium anodes provided with platinum group metal or mixed oxide conductor coatings and with perforations or mesh extending through the anodes so as to facilitate the escape of gas bubbles through the anode structure as well as around the edges of the anodes, are used.

It is, therefore, an object of our invention to provide an improved horizontal mercury cell and method of operation in which the cell is operated as a flooded cell with the brine substantially filling the cell box to the cover thereof and to the upper edge of the cell, where the top of the cell and the upper end Wall intersect.

Another object of our invention is to provide an improved horizontal mercury cell and method of operation in which the cell is operated as a flooded cell with the brine substantially filling the cell box to the upper edge of a horizontal cell, inclined between 0.1 and 1.9o from the horizontal.

Another object of our invention is to provide means for more accuratey spacing the anodes from the cathode during cell operation and to maintain this spacing substantially constant during the cell operation.

Another object of our invention is to provide means for maintaining a horizontal cell substantially filled with electrolyte so that the gas bubbles released at the anode will travel vertically through the electrolyte and diagonally from the low end to the high end of the cell along the bottom of the cell cover so as to maintain the electrolyte in a state of agitation and circulation within the cell.

Another object of our invention is to maintain a substantially constant electrolyte gap between the anodes and the cathode surface in a horizontal cell and to decrease the voltage requirements for equivalent cell performance.

Another object of our invention is to provide a horizontal electrolysis cell of the flowing mercury cathode type in which gas bubbles released at the anodes cause agitation and circulation of the electrolyte within the cell to provide substantially uniform temperature and composition of the electrolyte throughout the cell.

Another object of this invention is to use the electrolyte feed, and the agitating and circulating effect of the gas bubbles released at the anodes of a horizontal mercury electrolysis cell to carry solid impurities, such as broken particles of insulation, graphite and other solid impurities out of the cell with the depleted brine, where they can be removed by filtration or settling and to redissolve any calcium, magnesium or similar metals which have been deposited on the amalgam and carry them out of the cell in the brine-from which they can be precipitated outside the cell.

Various other objects and advantages of our invention will appear as this description proceeds.

Electrolysis cells of the type herein described may be used for various purposes such as the electrolysis of alkali metal salts and other materials. In the following description, the construction and operation of our improved cell in the electrolysis of sodium chloride to produce chlorine and sodium amalgam will be described as one embodiment of our invention. It will be understood, however, that this is only for the purpose of illustration and that the same apparatus and process may be used for the electrolysis of lithium, potassium, cesium and rubidium chlorides and bromides, for the electrolysis of barium and strontium chlorides and bromides, for the electrolysis of other salts which undergo decomposition under the electrolysis conditions which are produced in a horizontal flowing mercury cathode electrolysis cell and for other purposes, and that modiiications o f the preferred method and apparatus may be made within the scope of our inivention.

The term coated titanium anodes as used herein 1s intended to include anodes having a titanium or tantalum base or a base formed from titanium or tantalum alloys and having a conductive electrocatalytic coating over part or all of the said base, The term mesh is intended to include thin sheets of a valve metal or alloy (titanium or tantalum) in foraminous or expanded form, wire mesh, screen, rolled wire mesh and screen, punched and slotted sheets, spaced rods or half-round forms, etc.

In the accompanying drawings:

FIG. 1 is a sectional diagrammatical illustration of a horizontal type owing mercury cathode electrolysis cell in which the inclination of the base is between 0.1 and 1.9 from the horizontal, and preferably between 0.25 and 1.5 from the horizontal;

FIG. la is a cross sectional view substantially along the line la-la of FIG. 1; Y

FIG. 2 is a similar diagrammatic illustration of anothe embodiment of a horizontal mercury cell in which the principles of our invention are applied;

FIG. 3 is a perspective view of a dimensionally stable anode of the conductive coated titanium type, used in the cells of our invention;

FIG. 3a is an enlarged detail of the mesh configuration of the anode of FIG. 3;

FIG. 4 illustrates a horizontal type flowing mercury cathode cell, which is inclined between 0.1 and l.9 from the horizontal and which is provided with a sloping cell cover having a greater inclination from the horizontal than the base, to promote the ovv of gas bubbles through the electrolyte and circulation of the electrolyte;

FIG. 5 is a perspective view of the upper or mercury inlet end of the cell shown in FIG. 4, taken approximately at the line 5 5, with parts broken away;

FIG. 6 is a sectional View taken along the line 6 6 of FIG. 4;

FIGS. 7 and 8 are sectional views of a modified form of anode suspension;

FIG. 9 is a sectional view of a further modified form of horizontal mercury cell and anode suspension therefor;

FIG. l` is a view of another form,of dimensionally stable anode; and

FIGS. l1 and 12 are views of slotted and perforated graphite anodes which may be usedin the cells of our invention.

In the embodiment of the invention illustrated diagrammatically in FIG. 1, the cell comprises a base plate 1, a cover 2 and dams 3 and 4 forming a rectangular box-like construction. The base plate 1 may slope from 0.1 to 1.9 0r more from the horizontal. The substantially rigid cover 2, which may be liexibly connected to the side walls as shown in FIG. 1a, is located parallel to the base plate. The cover 2 may be flexible connected at its edges to the sides 3a of the cell, as indicated at 2a in FIG. la, and may have iexible inserts 2b connecting it to the rigid end sections 2c of the cell. Hold down bars 2d bolted to the cell walls hold the cover 2 on the cell. A dam and Weir 3 near the mercury inlet end of the cell and the dam and Weir 4 adjacent the mercury outlet end of the cell permits mercury to How into the inlet and from the outlet 6 and under the dams 3 and 4 while still retaining electrolyte within the cell box 7 between the dams 3 and 4. The

electrolyte -iills the cell substantially to the upper edge 8, leaving a small chlorine discharge space 13 at the upper edge or top of the cell. The anode risers 14 are sealed to the cover so as to prevent the escape of electrolyte or gas around the anode risers. Brine is owed into the cell through the inlet 9 which may be located any place along the top or sides of the cell. 'Ihe brine level, however, is maintained substantially at the level indicated at 10 by the use of a reservoir 11 at the top of the brine outlet 12. The brine tlows from the reservoir 11 through an outlet conduit .11a located on the level 10 of the brine. The anodes 13a, which are dimensionally stable foraminous titanium plates provided with an electrocatalytic coating on the faces of the anodes, are connected by anode riser connector bars 14 (diagrammatically indicated) with a suitable source of positive current and the cathode base plate 1 is connected to the negative pole of the circuit.

In operation, the mercury substantially stripped of the cathode product, which in the case of the electrolysis of sodium chloride brine consists of sodium, flows into the high end of the cell through the inlet 5 and the sodium mercury amalgam formed by the electrolysis process, flows from the low end of the cell through the amalgam outlet 6 to a suitable decomposer where the mercury is stripped of the sodium and recycled back to the high end of the cell. Brine entering through the inlet 9 lls the cell to the level 10 and to the upper edge or top 8 of the cell where the chlorine escapes into a small gas space 13 and is discharged through the chlorine outlet 15 above the top of the cell. If desired, an enlargement of the chlorine outlet, such as indicated at 17 in FIG. 2, may provide a greater space for the separation of the chlorine bubbles from the brine to avoid carrying foam and brine into the chlorine outlet. The sides 3a, top 2 and dams 3 and 4 forming the ends of the cell are covered with rubber or other suitable corrosion resistant material.

The gas bubbles released at the lower face of the anodes 13a rise vertically from around the edges of the anodes and through holes therein to the underneath portion of the cell cover 2 and ow along the bottom of the cell cover in a diagonal direction toward the upper end of the cell and promote a continuous agitation or ebullition and circulation of the electrolyte within the cell which carries solid impurities out of the cell with the outgoing brine and dissolves calcium, magnesium or other metals from the amalgam surface and carries these dissolved materials along with the brine out of the cell. `Outside the cell, these materials may be precipitated from the brine. The approximate path of travel of the gas bubbles within the cell is indicated by the bubbles b and the arrows in FIG. 1. Inside the cell, the electrolyte during electrolysis is kept in a high state of ebullition by the escaping gas bubbles.

In the embodiment illustrated in FIG. 2, the cell base 1b is inclined between 0.1 and l.9 or more from the horizontal. The cell cover 2c has substantially the same slope as the base plate 1b and is preferably parallel thereto. A dam and Weir 3b at the mercury inlet end of the cell and a similar darn and weir 4a near the mercury outlet and of the cell permits the mercury to row into the cell at 5a and along thevbase plate l'b to the amalgam outlet 6a and the dams 3b and 4a prevent electrolyte-from flowing out of the cell at either the mercury inlet or the mercury outlet end of the cell.

Brine entering the cell at 9a is maintained at a level higher than the highest point of the cell cover 2c by means of a reservoir or pressure feed to the line 9a and an eularged brine and chlorine outlet box 17 extending from side to side of the cell. The brine may be fed to the cell at any point along its length. The gas bubbles released at the anodes flow vertically upwardly from their point of release at the anodes to the underneath portion of the cell cover 2c and then diagonally along the underneath portion of the cell cover 2c into the enlarged brine outlet 17, as indicated by the bubbles b and arrows in FIG. 2. The spent brine is discharged through the brine outlet 18 and chlorine through the outlet 15. The anodes 13a are connected with a suitable source of positive current through the connector bars 14a and the cathode base plate 1b is connected to the negative pole of the circuit, so that current passes through the electrolyte between the anodes and the owing mercury cathode and the electrolyte is decomposed in the case of a sodium chloride brine into chlorine and sodium. Fluid tight seals (not shown) are provided around the anode connector bars 14 and 14a and the cell cover 2 and 2c. The anodes in FIGS. 1 and 2 are made of expanded metal, mesh or other foraminous structure, as illustrated, for example, in FIGS. 3 and 3a.

The gas bubbles b released in the lower end of the cell, illustrated in FIG. 2, travel vertically and diagonally upward along the underneath side of the cell cover toward the chlorine outlet box 17, as diagrammatically indicated, and encounter other gas bubbles released from the anodes further up the cell to cause a violent agitation and circulation of the electrolyte toward the upper edge of the cell. The introduction of the electrolyte toward the lower end of the cell, as shown at 9a, causes the electrolyte to ow over the amalgam adjacent the dam 4a where it dissolves calcium, magnesium and other metals from the surface of the amalgam and promotes better operation of the cell.

The anodes 20, illustrated in FIGS. 3 and 3a, comprise a titanium or other valve metal base a, such as tantalum, having an electrocatalytic conductive coating on the active faces thereof. The coating may contain a platinum group metal (i.e., ruthenium, rhodium, palladium, osmium, iridium and platinum), or an oxide of these metals together with other metal oxides, an electrocatalytic spinel or any other coating with conductive, electrocatalytic properties. The anode bases 20a have perforations or may be formed of a reticulated metal sheet such as shown at 22 in FIGS. 3 and 3a. They may be supported on supports resting on the bottom plate of the cell, or projecting from the side walls as hereinafter described, or suspended from lead-in conductors 35 passing through the cell cover. P-rimary conductor bars 23 and secondary connectors 23a convey the current from the cell bus bars and lead-in conductors 14 or 35 to the anode surfaces 22.

In the embodiment of the invention illustrated in FIG. 4, the cell Abase 25 is inclined between 0.1 and 1.9 or more from the horizontal. Channel iron sides and ends 26 form the side and end walls for the cell and a sloping cover 27 which may be of rubber lined steel or a flexible plastic material, is secured to the side walls by angle irons 28 and releasable clamping members 29 so as to permit ready removal of the cell cover from the cell box for inspection and servicing the interior of the cell.

Mercury enters the upper end of the cell through a mercury inlet box (not shown) and mercury amalgam flows out through the end box 30 into a decomposer 31 in which the mercury is stripped of its sodium and from which the purified mercury is returned to the inlet end of the cell. The cell cover 27 is supported from cross bars 32 and I-beams 32a supported on adjustable screw jacks 33 which are screw threaded into supports 33a secured to the channel iron sides 26 of the cell. The supports 33 are progressively longer from the outlet to the inlet end of the cell, so that the exible cell cover slopes upwardly from the outlet end to the inlet end of the cell at a higher angle from the horizontal than the slope of the cell base itself. Bus bars 34 are electrically connected to lead-in conductors 35, which are secured to the anodes 36. Fluid tight seals are provided around each lead-in conductor 35 and the cell cover 27.

The lead-in conductors 35 are also connected above the bus bars 34, to cross bars 37 supported from the I-beam supports 32a, which extend the length of the cell, by a telescopic or sliding connection illustrated in FIG. 6, so that when the I-beam supports 32 and 32a are raised the cross bars 37 will come into contact with the nuts 38 at the tops of the lead-in conductors 35, so that the entire anode construction and cell cover may be lifted from the cell. However, when the anodes 36 are reinserted into the cell, the anodes rest upon insulating supports 39 which lie on the cell base 25 and support the anodes at the desired spacing from the flowing mercury cathode on the base 25. In this position, the weight of the lifting frame 32-32a will not rest on the anodes, but the lead-in conductors 35 will slide upward through the holes in bars 37, so that the lifting frame is completely supported by the threaded supports 33 and the weight of the frame is not borne by the anodes themselves. The supports 39 extend longitudinally from end to end of the cell along the side walls as well as along the longitudinal interior of the base, so that they do not interfere with or break up the flow of the mercury along the base plate 25. While a flexible cell cover 27 is preferred, the cover may be made of rigid material and sloped upwardly at a greater angle than the angle of the base and substantially the same advantages as described for the flexible cell cover 27 may be secured.

Brine enters the cell through the line 40 and lls the cell to the upper level 41 indicated in FIGS. 4 and 5 and depleted brine is discharged from the outlet 42. Chlorine formed at the face of the anodes passes through the perforations in the anodes and rises vertically to the underside of the cover 27 and flows diagonally upward along the underside of the cover, as indicated by the arrows and by the bubbles b in FIG. 5, to the chlorine discharge space 41 and the chlorine flows out through the chlorine discharge outlet 43. Due to the greater slope of the cover 27 with reference to the slope of the base 25, the chlorine bubbles ow more rapidly along the underside of the cover 27 to the outlet 43 than in the case of the cells illustrated in FIGS. 1 and 2. The greater speed of ow of the chlorine bubbles along the underside of the cover 27 promotes a higher rate of circulation of the electrolyte within the cell and the entrace of the electrolyte at the upper end of the cell and the discharge at the lower end causes a counterow downward along the base of the cell which promotes a circulatory motion of the electrolyte Within the cell, which circulatory motion, together with the rising gas bubbles, provides a high degree of agitation and circulation of the electrolyte within the cell.

The bus bars 34 are connected to lead-ins 35, which may be surrounded by ceramic or titanium sleeves 35a inside the cell and a series of disconnect switches 44 mounted on a rod 45 running longitudinally of the cell permit short circuiting of the cell when it is desired to raise the cell cover or to otherwise inspect the cell or disconnect it from the normal circuit. The negative bus bars 46 are connected to the baise 25 of the cell through the connections 25a. The side and end walls 26 are insulated as is customary in the art.

While the embodiment of FIGS. 4, 5 and 6 has been described with reference to perforated, dimensionally stable anodes, graphite and particularly slotted and perforated graphite anodes may be used in this type of cell. Graphite anodes are not dimensionally stable, as they wear away during use but with a flooded cell and high agitation and circulation of the electrolyte, the temperature and composition of the electrolyte remains constant from end to end of the cell and the wear on the graphite anodes is substantially uniform from end to end of the cell. This, therefore, avoids the greater wear on graphite anodes which occurs at the hot, or mercury discharge end, of unflooded horizontal cells and gives better cell operation.

FIG. 7 illustrates a modified form of our invention in which the base 50, side walls 51 and cover 52 form the cell box and the anodes 53, which may be either dimensionally stable titanium sheets or graphite, are suspended on insulated projections 54 which extend inward from the side walls 51. Connectors 53a connect the anodes with a suitable source of current. A nickel insert 55 between the side walls 51 and the base 50 attracts mercury to it and insures that the mercury will wet the entire base plate 50 without the necessity for forming special mercury channels along the sides of the base plate.

FIG. 8 shows a further modification in which the anodes 53 are supported on insulating inserts 56 resting on the base plate 50 and placed adjacent the side walls 51. Channels 57 in the base plate provide a greater depth of mercury adjacent the side Walls and assure that this portion of the base plate will always be covered with mercury.

FIG. 9 shows how an existing horizontal mercury cell can be modified to operate as a liooded cell and provide for greater circulation and uniformity of the electrolyte therein. In this embodiment, the base plate 50 and side walls S1 are substantially as illustrated in FIGS. 7 and 8. The cell cover 58, which may be either flexible, or part iiexible and part rigid, is brought downward over the anodes, but is kept spaced therefrom by insulating rings 59 which surround the connectors 60 and is held in contact with the rings 59 by nuts 59a. The anodes 53 are suspended above the base plate by insulated projections 54 extending from the side Walls and spaced insulated inserts 61 resting on the base plate 50. The inserts 61 are placed within the cell so as not to interrupt the normal smooth flow of mercury from end to end of the cell base. A channel 62, lower than the top surface of the base 50, provides for a greater depth of mercury along the center of the base plate.

In the embodiment of FIG. .9, the cell is kept ooded with electrolyte up to the underneath portion of the cover S8. Gas bubbles rise from the anodes to the underneath portion of the cover 58, als indicated by the bubbles b, and then iiow into the gas release spaces 62 at each side of the cell. They also travel upwardly toward the high end of the cell along the bottom of cover 58 and are discharged from the cell through gas outlets located at the high end of the cell, thereby providing agitation and circulation of the electrolyte throughout the cell and providing an electrolyte of uniform composition and temperature from end to end of the cell. The cell is maintained .lled with electrolyte, except for the gas release spaces 62.

FIG. shows a reticulated metal anode 63 which may be titanium, tantalum or other valve metal coated with and electrocatalytic, conductive coating. Conductors 64 and 65 carry current to the anode 63 and a strengthening frame 66 extends around the entire edge of the anode 63 to provide strength and rigidity around the edge.

FIGS. ll and 12 show graphite anodes which may be used in any of the cells illustrated in FIGS. l to 9. In FIG. 11, the anode 67 is provided with grooves 68 which permit chlorine to enter the grooves and escape at the ends of the grooves, and in FIG. 12, the anode 69 is provided with holes 70 through which chlorine or other gaseous products of the electrolysis escape through the anode and into the electrolyte above the anode. The anodes of FIGS. 11 and 12 are provided with the usual graphite conductors (not shown) which conduct current from the bus bars to the anodes.

While we have illustrated several embodiments of our invention, it will be understood that various embodiments may be used and that changes in the embodiments illustrated may be made within the spirit of our invention.

W'hat we claim is:

1. The method of operating a horizontal flowing mercury cathode electrolysis cell having la base, a cover, and dimensionally stable foraminous metal anodes substantially parallel to the base, which comprises maintaining the cell at an inclination at which it can be filled with electrolyte substantially to the top thereof, maintaining an electrolyte feed level which fills the cell to the top thereof, maintaining a substantial depth of electrolyte above the anodes and between the anodes and the cover and causing the gas bubbles formed at the anodes to rise through the foraminous metal anodes and through the electrolyte above the anodes and flow along the underneath side of the cover to a gas discharge outlet adjacent to and above the top of the cell and discharging said gas bubbles above the top ofthe cell.

2. The method of claim 1 in which the base of the cell is maintained at an inclination between 0.1 and l.9 from the horizontal.

3. The method of claim 1 in which a reservoir forming the electrolyte feed is kept tilled with electrolyte substantially to the level of the top of the cell to maintain the cell iilled with electrolyte and excess electrolyte in said reservoir is discharged at a level above the top of said cell.

4. The method of claim 1 in which a gas discharge outlet box is provided above and adjacent the top of the cell and the gas bubbles are discharged adjacent the top of said gas discharge outlet box.

5. The method of claim 1 in which the cell cover slopes upwardly at a greater angle than the slope of the base, and the gas bubbles iiow upwardly along the sloping cell cover.

6. The method of claim 1 in which the anodes are supported on inserts on the cell base to maintain the spacing of the anodes from the cell base.

7. The method of claim 2 in which a rigid cell cover is provided along which the gas bubbles flow.

8. The method of claim 1 in which a flexible cell cover is depressed toward the longitudinal center of the cell and gas discharge spaces are provided adjacent the side walls of the cell and above the cell cover.

9. A horizontal iiowing mercury cathode electrolysis cell having a base inclined -between 0.1 and 1.9 from the horizontal, means to iiow mercury into and mercury amalgam out of said cell, along said base, a cover spaced from and substantially parallel to said base, means to iiow an electrolyte into and out of said cell, a gas release space at the top of said cell cover to discharge gaseous electrolysis products from said cell above the top thereof, dimensionally stable foraminous metal anodes spaced from said cover and from said flowing mercury cathode, means to pass an electrolysis current between the anodes and the liowing mercury cathode, means to maintain said cell filled with electrolyte substantially to the top thereof from Iwhich the gaseous electrolysis products are discharged and means to discharge gaseous electrolysis products from said cell above the top of the cell.

10. The cell of claim 9 in which the anodes are perforated and the gas bubbles released at the anodes pass vertically upward to the cell cover and diagonally along the underneath side of said cover to the gas release space.

11. The cell of claim 9 in which the anodes rest upon insulating supports, supporting said anodes a fixed distance from the flowing mercury cathode. I

l12. The cell of claim 11 having an anode lifting frame and anode lead-in conductors, which conductors have a sliding it with said frame.

13. The cell of claim 9 in which the anode face comprises a perforated valve metal sheet from the group consisting of titanium and tantalum having a coating thereon, containingy conductors from the group consisting of platinum group metals, platinum group alloys, platinum group metal oxides and other metal oxides.

14. The cell of claim 9 in which the cell cover slopes upward from the base at a greater inclination than the inclination of the base plate and the gas release space is at the highest portion of said cover.

1S. The cell of claim 9 in which a reservoir with an overow outlet maintains the electrolyte at a level which iills saidcell to the top thereof.

16. The cell of claim 9 in which'the cover is provided with an upwardly projecting enlarged gas release space above and adjacent the upper edge of said cell and means to discharge gas and electrolyte from said enlarged gas release space.

9 l0 17. The cell of claim 9 in which a exible cell cover is 3,390,069 6/ 1968 Utsugi et al. 204-250y X provided and the cover is depressed in the longitudinal 3,308,044 3/ 1967 lBarbato et al. 204-219 X center of the cell below the cell side walls, the electrolyte 3,441,492 4/ 1969 Fornoni 204-250 X is maintained at a level where it contacts the cover and 3,409,519 11/1968 GallOIle et al. 204- 99 gas discharge spaces are provided along the side walls of 5 FOREIGN PATENTS the ce and above the cover' 297,826 6/1954 switzerland 204-250 References Cited `650,243 2/1951 Greet yBritain 204-219 UNITED STATES PATENTS HOWARD S. 'WILLIAMS, Primary Examiner 3,499,829 3/1970 Messner et e1. 204.220 x 10 D. R. VALENTINE, Assistent Examiner 3,535,223 10/ 1970 Baecklund et al. 204-275 U.S CLXR.

3,627,652 12/1971 De Nora 204-220 X 2,316,685 4/1943 Gardiner 204 99 204'219, 220, 225, 250, 275, 278, 284, 285, 290 F- 

